As congested traffic conditions become a daily occurrence, it becomes increasingly important to accurately analyze signalized intersection operations. The capacity of individual movements at signalized intersections is dependent on various factors, chief among which are the effective green time (depends on lost time and green time) and the saturation flow rate. There has been very limited research on the components of effective green time, namely start-up lost time and clearance lost time (alternatively, extension of green). Based on findings of this study, it is suggested that the clearance lost time be calculated as the sum of the all-red clearance interval and a portion (50% to 75%) of the yellow change interval. This will result in significantly higher total lost times for movements than the three seconds default value recommended in the Highway Capacity Manual (Transportation Research Board, 1994), and will thus impact capacity and subsequent calculations. (A)
Abstract